Under Water

NOTES AND OBSERVATIONS FROM THE
WORLD UNDER THE WATERLINE

CONTENTS

Introduction ............................................. 1 Bigger Brain Not Always Smarter Brain 50
The Red Sea: Past And Present ................2 Using Natural Body Markings To Identify
The French Mediterranean: Damaged But A Shark....................................................51
Not Lost ....................................................5 Eco Aqueduct In North Holland............ 53
A 3d-Scan Library Of All Fish Species. ... 8 Bass And Bream From The Desert ........ 54
Visualizing Sharks During Rushing Hour The Tourist Value Of A Shark................ 55
................................................................ 10 How To 'Catch' A Shark ......................... 58
What Makes Dolphins And Swordfish Such Being A Senior Diver..............................60
Fast Swimmers? ..................................... 12 The Florida Sirens...................................61
To Kill A Lionfish ................................... 14 Shark Doc, Shark Lab ............................ 64
The Bahamas: A String Of Pearls In The The Benefits Of Baiting.......................... 66
Blue Ocean.............................................. 16 Hammer Is Hot...................................... 68
Nurse Sharks: ‘Lazy’ But Efficient Sexism In Diving? .................................. 70
Survivors ................................................ 18 Underwater Photography Websites....... 72
Mangroves. The Forgotten Habitat........ 19 Are Guys Better Photographers Than
Fear Of Large Predators May Affect The Girls?...................................................... 73
Food Chain. ............................................22 Are Divers Sensation Seekers? .............. 75
The Shark In Captivity ...........................23 Wildlife Crime Is Booming Business ......77
Greenland Sharks Can Live At Least 300 Stereotyping The Wild Animal As A
Years .......................................................24 Monster.................................................. 78
Facing The Abyss: Free Diving And Its Models And Mermaids ..........................80
Risks .......................................................26 Unhappy And Happy Pigs...................... 82
Life Of A Goby ....................................... 30 Live-Aboard Or Resort?......................... 84
The Dolphin, Marvel Of The Sea ............32 The Health Of Our Oceans..................... 85
The Amazing Cuttlefish ..........................35 Visualizing The Underwater World .......88
The Pygmy Seahorse ..............................37 Nostalgia (1) The Medium Format Camera
Olfaction Contributes To Pelagic ............................................................... 90
Navigation In Sharks..............................39 Nostalgia (2): Remembering Cousteau . 92
Cheating For Survival; The False Cleaner About Underwater Photography Contests:
Fish ........................................................ 40 Winning A Prize Or Not......................... 93
The Ways Of An Octopus ....................... 41 Bass And Bream From The Desert ........ 95
The Sperm Whales Sonar Head .............42 Climate Change, Protection Of Our
About White And Black Tipped Sharks..45 Environment And Biodiversity .............. 97
The Sharks Electrical Sense ...................47
Hearing And Sensing Under Water.. 49

INTRODUCTION

This book contains a selection of notes and articles from my website of the last two
years. The initial idea was to present only my underwater pictures. But later I decided
to give the site a somewhat broader scope. I added a new button ‘Test and
Techniques’ with various subcategories like macro-photography, strobes & light, test
pictures, models, domes, to name just a few. Realizing that very much had already
been said on these matters by people with much more expertise than myself. So I

considered it as my pleasant task to use their
expertise, but also add some information based on
my own ideas. My primary interest has always been
wide-angle, in particular fisheye lens photography. I
feel that the fisheye is the best way to capture the
underwater world in a most comprehensive way. It
provides details of fore- and background, small as
well as large subjects. My personal choice was the
Tokina 1o-17 fisheye, with a 1.5 crop Nikon SLR.
Many shots taken with this set up can be found in the
Photo Albums section of my website 1 . I was
pleasantly surprised that Alex Mustard shares my
view, when he declares in his new book (pg 26): ‘The
fisheye lens is as essential to underwater photography as water is to life on earth!’
Later, I added two more buttons ‘Biology’ and ‘Blog’, focusing not primarily on UW
pictures and its techniques, but on more general aspects of the underwater world.
This included topics like: the behavior and biology of fishes, diving tourism, free
diving, baiting of sharks, dolphins held in captivity, and the health of our oceans.
Some of them were just ‘snapshots’, others more elaborate articles. I was also happy
that these short notes and articles attracted a substantial number of visitors. Then I
decided that bundling them in a little book might be a good way to express my
appreciation for their interest. The book is now available in the format of an E-book
(free).

Albert Kok.
Amsterdam, August 2016

1 www.albertkokuw.nl

1

THE RED SEA: PAST AND PRESENT

The Red Sea is the world most northern tropical sea, squeezed between two continents
of arid land and deserts. Geologically its considered to be a crack in the large and slowly
shifting continental plates of Africa and Eurasia. It is 1200 miles long but only 350 miles
wide at its widest point, with an average depth of around 1500 ft, and a long central
median trench of a least 7000 ft. One would not expect to find such a deep crystal-blue
sea in the middle of those immense heat-blasted deserts of rocks and sand.

Visitors of an UW photo workshop in North Egypt, led by Alex Mustard in yellow T shirt. In
front in blue, Eleonora Manca, Alex current wife. The author: fifth left back row.
For underwater photographers the Red Sea is still one of the most interesting places on
our planet to visit. The underwater world is similar to that of the Indian Ocean and the
Maldives. Its crystal clear water, rich and colorful coral reefs and abundance of fish
make it the ideal environment for either macro or wide-angle shots of all kind of
objects. There are tiny cleaner shrimps, gobies, reef fishes, sharks, shoals of snappers,
wrecks, soft and stony corals, steep drop offs and caverns. The variety of reef fishes that
have chosen the coral and its crevices as a habitat is astonishing: the different species
of butterfly fishes are just one example. The contrasting colors (especially yellow and
red objects on the foreground against a blue background) and the beautiful light make
the Red Sea a perfect place to play around with techniques like mixed-lighting and
CFWA (Close Focus Wide Angle).
Egypt area In the 70ties and 80ties the North-Western Red Sea was visited by only a
'handful' of divers. Some people not even knew of its existence! Diving tourism was still
in its infancy, and towns like Sharm el Sheikh and Hurghada were sleepy and friendly
villages with only a few hotels and visitors. Some local dive clubs, mostly run by

2

Europeans took their clients on rented fishing boats to the reefs in the neighborhood,
such as Ras Muhammed in South Sinai, the wrecks in the street of Ghubal, or the Abu
Rimathi, Carless and Giftun island reefs near Hurghada. The reefs in Southern Egypt
were still 'white spots' on the maps. Mass tourism only started ten years later around
1990. First by visitors of the beaches, and later also by scuba divers when larger vessels
departing from Sharm or Hurghada took divers to more remote islands that later
became famous ‘hotspots’; the Brothers, Elphinstone, Daedalus and deeper in the
south: Rocky Island, St John’s reef, Zabarghad, Fury Shoals and Shab Abu Fendera.
Like tourism, UW photography in these years was still in its infancy. Most popular
cameras were the Nikonos (successor of of the Calypso, designed by Cousteau) and
the medium format Rolleimarin housing (designed by Hass) with a Rolleiflex 3.5 F
inside. Both systems used analog roll films, allowing only a limited number of
exposures.
Another ten years later (say from 2000 on) diving resorts and hotels started to grow like
mushrooms in the desert along the entire Egyptian Red Sea coast. Often financed by
rich Egyptian or Saudi businessmen. The advent of luxury live-aboard catering for the
growing influx of divers put an end to the small scale diving trips of former years. But it
also led to more crowded diving sites and packs of diving boats lined up along the reefs
with their pick-up Zodiacs racing around. In the same period underwater-photography
was lifted to a higher level. Two factors played a role: the advent of modern digital
cameras with interchangeable lenses, and the live-aboard photo workshops. Best known
-if not famous- were the ones led by Alex Mustard in the Sharm area (see picture
above), but later on also at more southern locations in Egypt. A live-aboard workshop
offers more comfort for divers and photographers, and the certainty that one will we
dropped at interesting sites. But is also means more safety than the hotels, bars and
restaurants in crowded towns like Sharm,
that sadly enough have become
potential targets of political terrorists in
our modern times.
Fishery cannot supply enough fish for the
growing populations. This holds for
countries like Egypt, Saudi Arabia and the
southern states of the Arabian
peninsula, that still depend to a large
extent on fish caught in the Red Sea. Their
catch of course cannot compete with that
of the fishing industries that operate in
the Atlantic Ocean. But there are
complaints of pollution affecting the
fishing areas in the Saudi regions, similar to those in the Atlantic ocean. And then there
is the controversial shark finning by fishermen along the southern Arabian peninsula
selling their product via Dubai to the Asian market. Nevertheless, large parts of the Red
Sea's underwater wilderness still exist, and there are still magnificent reefs to visit in
Egypt, as well further south in the Sudan.

3

Red Sea: deeper south Sudan was once a state under former British-Egyptian
administration, but is now a republic. The Umbria wreck, Sanganeb and Shab Rumi
atoll islands, not so far from Port Sudan had already become legendary underwater
locations in the late 70ties. Shab Rumi was the site of Jacques Cousteau’s underwater
village Precontinent II in the early 60ties. I myself became a regular visitor of the
Sudanese reefs in the years between 1983 and 1990. Our trips were organized by a small
London tourist office and led by Jack Jackson, a lanky black bearded Londoner. Flights
from London were often hectic with several stops in Cairo, Khartoum to Port Sudan,
separated by long intermissions. On one occasion we even had to travel 500 miles in a
crowded not air-conditioned bus from Khartoum to Port Sudan, after a strike of flight
personnel. From Port Sudan Jack took us, usually a small group of divers, on a former
military vessel to Sanganeb’s light house island. The island is a large atoll, a real
underwater paradise with massive coral tables (Acropora) and soft coral trees
(Dendronephtya) expanding their splendid branches when there is a current. Here we
camped on foam mattresses in the open air for one or even two weeks. Two small
compressors provided the air to fill our tanks.

About sharks and feeding
sharks. In recent years some shark
species, like the Oceanic shark have
even become easier to approach than
in the pioneering years of Hans Hass
and Jacques Cousteau. In Egypt,
Oceanics show up regularly at the
Brothers and Elphinstone, despite the
fact that feeding sharks is prohibited. I
think we must have been one of the
first groups of divers that started
baiting (or feeding) the grey reef
sharks at Sanganeb without a cage in
my Sudan period. I must also mention a German diver called Herwarth Voightman, who
probably was the very first shark feeder without a cage. Herwarth started to train grey
reef sharks in 1978 by hand feeding them on one of the Maldives islands. He also had a
feeling for spectacle, and let his beautiful daughter Bine feed the sharks from her
mouth. Our method was less spectacular, but probably more effective from an
UW photographers perspective. A piece of dead fish was hidden under a stone, sea fan
or attached to a heavy object. Grey reef sharks were our most frequent visitors, but
sometimes other species like the silvertip, schools of hammerheads and silky sharks also
moved in.
After the political coup in 1989 that led to establishment of a Muslim state and
legislation in Sudan, it was not allowed to camp on the island anymore. But years later,
its reefs near Port Sudan became accessible again for larger live-aboards leaving from
Sharm or Hurghada. In 1990 Sanganeb island was declared a national marine reserve.

My Red Sea diaries 1981-1991

Coral Kingdoms. Cark Roesler. 1986. Abrams publishers, N.Y

Reef. A Safari through the Coral World. Jere4my Stafford-Deitsch.1991. Headline. London

THE FRENCH MEDITERRANEAN: DAMAGED BUT NOT LOST

In the French Mediterranean lies a chain of islands, 15 miles south of the coastline of
the towns of Hyeres and Le Lavandou (see picture below). The French gave it the
poetical name ‘Les Isles d’Or’ (Golden Islands). They consist of three big islands:
Porquerolles, Port Cros and I’le du Levant and a couple of smaller rocky satellite
islands: I. Gabaud, I. Rascas and I. Gabiniere around Port Cros.
The area around Port Cros was declared a French national park in 1963 on the

initiative of Philip Tailliez, a friend of
Cousteau. The state is now the sole
owner. Later, a part of the bigger
island Porquerolles was included in
the National Park (also encircled in
green, at the left). Diving tourism is
booming in the summer month when
you will find numerous boats along
the peninsula of Giens on the
mainland as well as the smaller
islands of the national park.
In the summer the weather is dominated by a south-westerly wind that normally
comes with sunny weather and an agreeable temperature running in the 80ties. But
occasionally, a cold and fierce wind, the Mistral drops in after a depression. The
Mistral arises in the high pressure Central Plateau in the middle of France and then
forces itself southwardly trough the Rhone valley until it reaches the low pressure
Mediterranean sea near Marseille. In then spreads out sideward to follow the Eastern
and Western coastlines, gradually losing its force. The dry and cold mountain air of
the Mistral leads to a cloudless blue sky and a temperature drop of the air, as well as
the water, when turbulence mixes warmer surface water with deeper colder water.
There are several wrecks to visit in this area. To name just a few: the Donator (or:
Prosper Schiaffino, depth 45 m), the Michel C. (35 m) and Le Grec (45 m). Diving to
the wrecks is only possible with a calm sea, and one must always be aware of currents
and the depth of their locations, which bring divers easily within the decompression
zone.
Despite the beauty of its rocky and fertile coastline, the Mediterranean is a relatively
poor sea. Cousteau already wrote ‘La Méditerranee est belle mais pauvre’ . This holds
for its fish colonies that cannot compare with those of the Atlantic as well as the
amount of nutrients in the water. An ecosystem that can survive in these condition
is called oligotrophic: this implies a slow growth and rate of metabolism of
organisms, and a low density of the fish populations. In the past coastal waters and
beaches near the bigger cities of Corsica as well as the Cote d'Azur suffered from
pollution from the sewers that dumped their content directly in the sea. Luckily, this
has been improved some 30 years ago. The presence of the sea grass fields of
Posidonia oceanica is often considered as an index of the health of the
Mediterranean. One estimates that the size of these fields has been reduced with

5

around 20% in the last century by water pollution and boats anchoring in coastal
areas. Overfishing has also threatened larger fishes. An example is the Dusky
grouper (Epinephelus marginatus) that is still considered an endangered species in
the Mediterranean, especially in Spain (see picture at left).

The Dusky grouper is a
protogynous hermaphrodite, i.e.
the young are predominantly
female but transform into males as
they grow larger. But since it is
also a favorite dish on Mediterra-
nean tables, they have been hunted
down without mercy both by
fishermen and spear gun adepts
until only a few were left in the
70ties. One of the blessings of the
National park of Port Cros was the
miraculous come-back of grouper
colonies, that now consist of several
Dusky grouper (Epinephelus marginatus)

hundred individuals. Occasionally they even show up along the protruding points of
the Peninsula of Giens. I managed to bring in some groupers very close to the camera
by using my ‘personal chumming device’; a little plastic bottle filled a liquid sardine
substance. The trick is to squirt a small cloud of chum in the water, only about 10 cm
wide, but sufficient to stimulate the grouper's refined olfactory system even when it is
still some meters away. After a couple of visits they will approach you even without
using the device. One should be aware however that the use of this gadget in areas
where baiting is prohibited may still be considered as an offence.
In the Mediterranean you will not find the variety of hard and soft corals of its
neighbor, the warmer Red Sea. It does however have its own specialties: colonies of
yellow anemones (Parazoanthus axinellae see picture below) often found on cave
walls, and gorgonians like Paramuricaena clava and Eunicella, mostly at walls
exposed to a current. In shallower waters near the coast one will still find the sea
grass fields of posidonia oceanica, often a hiding place for the cuttlefish sepia
officinalis, the red anemone actinia aequina (Beadlet anemone) and anemonia
sulcata ('spaghetti anemone') in the intertidal zone. The bigger ceriantus
membranaceus, a large solitary anemone can be found on deeper and muddy sandy
floors. Its polyps detract rapidly into its tube if you get too close. And then there is
the tube worm spirograph spallanzani with its beautiful spiral crown, another
favorite target for close up photographers. Around the smaller islands of the park like
Gabiniere you can occasionally meet schools of the barracuda (sphyraena
sphyraena). And there are numerous smaller fish along the walls and crevices of the
islands. Here follows a selection of species that you can still see when you dive
regularly in the area.

6

Mullets (mullus barbatus and surmulletus,
rouget in French), moray eel (muraena
helena), scorpionfish (rascasse: red:
scorpaena scrofa, brown: scorpaena
porcus), wrasses like the rainbow wrasse
(coris julis), peacock wrasse (thalassoma
pavo) and crenilabrus, the lovely anthias
anthias, the little black damselfish
(chromis chormis), several species of
blennies mostly in shallow rocky areas,
schools of smaller sea breams like diplodus
vulgaris and sargus, sarpa salsa, the
bigger dentex, and of course the octopus
vulgaris. To name just a few species that
were part of the original Mediterranean
biotopes, and have now returned in greater
number in areas protected from pollution and overfishing. Difficult to spot, but
present in the area are rays, the ovipari dogfish (scyliorhinus, rousette In French)
and dolphins. Some 30 years ago Cousteau spoke of the Mediterranean as the
‘wounded sea’ (La Mer Blessée). But it is good to learn that the damage of
Mediterranean sea caused by human neglect can be repaired by human care. At some
locations this has even resulted in a return of the former paradise.

Source:
The Hamlyn guide to the Flora and Fauna of the Mediterranean Sea. A.C. Campbell.
London

7

A 3D-SCAN LIBRARY OF ALL FISH SPECIES.

To understand how humans and non humans move around in their world, knowledge
of the skeleton is essential. It’s easier to understand how a bird flies if we know the
internal structure of its flying apparatus: the bones, tendons, joints and muscles. This
biological knowledge can be useful for engineers, for example to design aircrafts that
are not only lighter but also have better aerodynamics. Biologically inspired technical
design is called biomimetics. A fascinating application are biorobots: robots that
mimic the way real animals move and interact with the environment (see insert, left
showing Pleurorobot: a salamander-like robot that mimics its biological counterpart.

Pleurorobot 3 D scan of fish skeleton

Also for creatures that live in the sea knowledge of the structure of their internal
skeleton is important to understand how they move, make swift turns, burrow, prefer
to stay in shallow water or in the deep etc. This knowledge can then be used to mimic
movements of fishes, for example in filmed animations of fishes or in modeling a
robotic sea slug. Adam Summers (Adam P. Summers – [email protected]) is a
biologist at the University of Washington in the Biology department and School of
Aquatic and Fisheries Sciences. He has set himself the goal to create a digital library
with 3-D images. using CT scans of all 33,000 species of fish in the world (see insert,
right part). Summers says it can be done in about three years by scanning multiple
fish at the same time. His fish odyssey began 15 or more years ago with a question:
‘Why are sharks and rays able to move about like other fish even though their
skeletons are composed of cartilage and not bone?’
Summers has a background in engineering and mathematics and an interest in the
evolution of non-human animals and how they move in their environment. ‘I love
the idea of getting all this stuff up on the Web for anyone to access for any purpose'.
'To allow the general public and every scientist out there to just download these data
is fabulous', Summers says. He even uses a 3D printer to make physical models of
these skeletons (just think of that transparent model of a stingray on your desk!). His
mission is to ‘use the natural world and the sea for inspiration for new materials
and new ways of doing things’ For example, he shares his experience working with

8

the animation studios, where he was asked by animators to judge separate frames
and distinguish real from computer created fishes. He also supervised animators on
how a certain fish would behave and move around in films like as 'Finding Nemo'
and Disney's new product ‘Finding Dory'.

Links:
http://dx.doi.org/10.1098/rsif.2015.1089
http://news.nationalgeographic.com/2016/07/ct-scan-fish-digitize-x-ray-ocean-
world-sea-river-lake/
https://osf.io/ecmz4/wiki/Fishes/
http://www.universityherald.com/articles/32193/20160620/university-
washington-professor-adam-summers-advises-pixar-animators-disney-finding-
dory.htm

9

VISUALIZING SHARKS DURING RUSHING HOUR

We are all familiar with the principle of ultrasound used to locate objects. Bats,
dolphins and whales emit pulsed sounds or 'clicks' for echolocation to detect their
prey or to communicate, submarines emit sonar pulses to detect enemy submarines.
Ultrasound imaging or sonography is a popular tool in medicine to visualize
muscles, tendons or internal organs with real time tomographic (sliced) images.
Future mothers often use a 'funscan' to visualize their fetus. Ultrasound devices

operate with frequencies from 20 kHz up to
several gigahertz, much above the upper audible
limit of human hearing.

Left: Acoustic camera recorded image of a shark
moving through the sonar unit's field of view.

An interesting recent application of ultrasound is

the acoustic camera to observe the movement

and behavior of sharks transiting narrow sea

passages. Douglas J. McCauley and coworkers

from the University of California Santa Barbara

used a ultrasound sonar device called DIDSON

(Dual-frequency Identification Sonar) to

‘acoustically gate’ a portion of sharks moving in

and out a corridor of Palmyra Atoll. Palmyra is an

5-square-mile ring of coral halfway between

Hawaii and American Samoa, and a sanctuary for

a variety of mobile species including sharks, manta rays and turtles. The area is

protected as a U.S. National Wildlife Refuge and its lagoon and surrounding coastal

waters are declared ‘no-take’ zones.

The DIDSON submersible sonar unit is small and nearly neutrally buoyant in water.

The unit permits high-resolution digital imaging of objects within the sonar's field of

view. It is especially useful in low-light, turbid waters to study movements of fish or

marine mammals in environments where fishes are physically constrained through

natural or artificial environmental gateways. Or harbor entries, ship wrecks and other

fish habitats. The weak point however is that the device does not permit to identify

individual species, although it is possible to distinguish fishes on the basis of their

global shape and size.

The acoustic camera near-continuously monitored a 42 m3 section of channel space.

The maximum linear distance visualized by the acoustic camera was 10 m.

Investigators mainly tracked movements of black tip sharks (C. melanopterus), the

most common shark observed in Palmyra's lagoons. They found that shark density

and directionality of travel through the channel at night was more than three times

greater than that of sharks moving through by day. Peaks in shark densities (‘rushing

hours’) were specifically recorded during the post-dusk period (1909–2009 h).

10

Source and links:
Moursund, R. A., Carlson, T. J., and Peters, R. D. 2003. A fisheries application of a dual frequency
identification sonar acoustic camera. – ICES Journal of Marine Science, 60: 678–683.
http://www.sciencedirect.com/science/article/pii/S0022098116300855
http://www.news.ucsb.edu/2016/016952/rush-hour-palmyra-atoll

11

WHAT MAKES DOLPHINS AND SWORDFISH SUCH FAST SWIMMERS?

Dolphins are known to be very fast swimmers with a low energy expenditure. In the
past this has puzzled marine biologists because they believed that the muscle power
of the dolphin was not sufficient to overcome the big ‘drag’ or resistance caused by
the body moving through the water. The puzzle was even called the Gray’s
paradox after the British Zoologist Sir James Gray. Gray thought that the dolphins
skin had special anti-drag properties. In 2008, 75 years, later Timothy Wei with
Frank Fish, a biologist at West Chester University in Pennsylvania and Terrie
Williams, a marine biologist at the University of California, Santa Cruz solved the
paradox using cutting edge technology .
A factor that was overseen by Gray in 1937 was that muscle power of the dolphin is
largely used to undulate its body, more specific to produce powerful up and down
sweeps of its tail (‘flukes’) causing hydrodynamic vertical forces and

‘drag’ turbulence behind the tail (see
picture, top panel). So the great
propulsive forces of the dolphin
seemed to resulted mainly from
movements of its tail. But up to
recently there were no ways to
measure directly the force exerted by
a dolphin and the forward thrust of
its body. The method Wei a.o.
used came from aerospace and is
known as Digital Particle Image
Velocimetry (DPIV). DPIV measures
were based on a analysis of video
recordings of micro air bubbles
injected in a pool with swimming
bottlenose dolphins (Tursiops
truncatis). DPIV can capture up to
1,000 video frames per second. They
found that the dolphin exerted
approximately 200 lb of force every
time it thrusts its tail – much more than Gray hypothesized – with at peak force
between 300 to 400 lb. Without going into all the technical details: ‘dorsoventral
oscillations of the flukes of the dolphin produced pairs of counter-rotating vortices
during each propulsive cycle. One vortex was generated for each upstroke and each
downstroke of the tail’( (see picture, upper panel)
Speedy swordfish. Swordfish (Xiphias gladius) belong to the Billfishes that also
comprise Sailfish and Marlins (see picture, lower panel). Swordfish swim at even
higher speeds and accelerations than dolphins, and alleged to reach speeds of 100
km ph. What makes swordfish such fast swimmers? Here the anti drag properties of
its body, in particular the head seem to play an important role. Emeritus professor
John Viderel from the Groningen University in the Netherlands already suspected

12

that the rapier shaped head (‘bill’) of the swordfish might reduce the amount of drag
pulling on the fish as it sweeps through the ocean. Roughness at the tip of the bill
could generate micro turbulence in the water, to make it ‘thinner’ and reduce the
drag, which improves performance. Later, he took two dead swordfish he got from a
Corsican fisherman home, and placed them in a medical MRI scanner. He then
discovered a network of vessels in a thin spot near the nose that were connected to an
oil gland. Videler believes that the oil, in combination with microscopic rough
projections on the skin, might produce a surface that is super water-repellent and
could reduce the drag on the animal by over 20%. So according to Viderel the oil
layer, in combination with the denticles, ‘creates a super-hydrophobic layer that
reduces streamwise friction drag and increases swimming efficiency.’

Sources:
Bale et al. (2014) Gray's paradox: A fluid mechanical perspective" Nature: Scientific Reports
4: Article
Fish, F. E., Legac, P., Williams, T. M. & Wei, T. Measurement of hydrodynamic force
generation by swimming dolphins using bubble DPICV. J. Exp. Biol. 217, 252–260 (2014)
Videler, J. J., Haydar, D.,Snoek,R.Hoving, H.-J. T. and Szabo, B. G. (2016). Lubricating the
swordfish head. J. Exp. Biol. 219, 1953-1956.
Lee, Hsing-Juin; Jong, Yow-Jeng; Change, Li-Min; and Wu, Wen-Lin (2009) "Propulsion
Strategy Analysis of High-Speed Swordfish" Transactions of the Japan Society for
Aeronautical and Space Sciences
http://www.dutchnews.nl/news/archives/2016/07/nasal-oil-gland-helps-swordfish-swim-
faster-says-new-study/

13

TO KILL A LIONFISH

In the Red Sea lionfish species such as Pterois volitans, Pterois miles and Pterois
radiata are one the most popular subjects for the beginning underwater
photographer. They can make beautiful shots, with suitable lighting and some
branches of soft coral as a colorful background. The lionfish is not shy and easy to
approach, it may turn towards the invader spreading its beautiful pectoral fins
making it look even more impressive. Lionfish species are native to the Indo-Pacific,
but are now established along the southeast coast of the U.S., the Caribbean, and in
parts of the Gulf of Mexico. One speculates that this all might have started with
retired aquarium enthusiasts releasing them in Florida waters.
Since lionfish are not native to the Atlantic, they have very few predators which
caused their number to increase dramatically, especially through the South Florida

Estuaries, the Gulf of Mexico
and the Caribbean Sea. A
lionfish can eat enormous
quantities of juvenile fish: an
estimation is that a single
lionfish can reduce juvenile fish
populations by 79% in just 5
weeks. They also reproduce
rapidly, spawning every 4 days
year-round and producing
around two million buoyant
gelatinous eggs per year. In the
Indo-Pacific Oceans were
lionfish are native, groupers,
sharks and coronet fishes are known to prey on lionfish. In the Atlantic however,
groupers are severely overfished and struggling to fill this role. Their growth in
Caribbean waters is therefore difficult to control.
NOAA researchers have concluded that invasive lionfish populations will continue to
grow and cannot be eliminated using conventional methods. Marine invaders are
nearly impossible to eradicate once established. One currently used method is based
on the principle ‘Eat Em to Beat Em’. So on some islands the hunt of the lionfish is
encouraged and licensed. At the island of Bonaire Scuba divers can follow a crash
course in effective harpooning of the lionfish, and PADI has developed a “Lion
hunter’ certificate to stimulate the hunt. It’s even possible to eat your catch called
‘Lionfish burgers’ afterwards in special beach BBQs. Eating lionfish is considered be
the "ultimate in guilt-free eating - delicious, nutritious and eco-conscious".
But likely these hunting & eating practices are impractical and probably unsuccessful.
So the only solution might be to let nature take care of itself, and hope that on
the longer term the disturbed fish population will restore itself. Calling the lionfish
invasion the 'greatest threat of our century' may be pushing the argument a bit to
far. Such a statement seems more appropriate for the massive pollution and
overfishing of our oceans. That could be one of the factors underlying this sudden

14

invasion of Pterois. In areas were sharks are abundant such as the Bahamas and
Honduras, sharks may switch to a different menu, and start eating the lionfish, even
when it comes second to their favorite natural dish. For instance if the lionfish are
outnumbering the native species in their territories. In Roatan Marine Park of the
coast of Honduras dive masters are now even training sharks to hunt lionfish, with
moderate success. Finally, a comeback of other large predators like the Nassau and
Goliath groupers in the Western Atlantic could also help to bring the lionfish
population down to acceptable proportions.
Lionfish invasion in the Mediterranean? Mediterranean seawater
temperatures are steadily increasing, and alien species are spreading, causing
community shifts and tropicalization. Alien species have mainly invaded the eastern
basin of the Mediterranean, probably through the Suez canal. Recent enlargement of
the canal coupled with sea surface warming is raising concerns that this problem will
get worse. Examples of some alien species are the pufferfish (Lagocephalus
sceleratus) and the lionfish (Pterois Miles). P. miles was first recorded in 1991 off
Israel, but recently seems to have now colonized almost the entire south eastern
coast of Cyprus in a period of only one year. Both species feed on local species in the
Mediterranean taking advantage of their naiveté, and may threaten its biodiversity in
the coming years. The pufferfish eats the economically important Sepia
officinalis and Octopus vulgaris. One hopes that native groupers such as Epinephelus
marginatus will learn to prey on lionfish and control their invasion.

Links:
http://sailorsforthesea.org/programs/ocean-watch/lionfish-invasion
http://www.npr.org/sections/parallels/2014/11/10/361155911/why-divers-in-bonaire-are-so-
eager-to-kill-the-beautiful-lionfish
http://news.nationalgeographic.com/news/2011/03/pictures/110404-sharks-lionfish-alien-fish-
invasive-species-science/
http://lionfish.gcfi.org/index.php
http://mbr.biomedcentral.com/articles/10.1186/s41200-016-0065-y

15

THE BAHAMAS: A STRING OF PEARLS IN THE BLUE OCEAN.
The Bahamas are a chain of hundreds of islands in the North Western Atlantic
consisting of atolls and cays: heaps of loose sediment piled up by the Ocean streams.
The islands lie on top of shallow limestone platforms -or Banks, that rarely go deeper
than 25 meter (see picture: arrows show the three major shark locations from North
to South: Tiger Beach, Bimini and Cat island). The Banks were presumably still
exposed to air in the Ice age, but then gradually submerged below the rising sea
level. Florida belonged to the same limestone formation, but remained above the
rising sea level.

The Bahamas. Light blue area: the shallow banks, red arrows: the three shark
sites from north to south: Tiger Beach, Bimini and Cat Island.

The Bahamas were discovered by Columbus in 1492. Probably Cat island was his first
stop on his way to the New World which was then baptized as San Salvador. In his
diary Columbus described the Lucayans as the first inhabitants. They were
were related to the Tainos, indigenous people that inhabited most of the Caribbean
islands, and who probably descended from of Indian tribes from the Amazon
territory. One believes that the Tainos sailed from the Caribbean islands to the
Bahamas in the 11th century. The Spanish started capturing Lucayans as slaves in the
decades following Columbus' arrival. Most of them were deported from the Bahamas
to Spain. Much later, in 1718 the Bahamas became a British Crown Colony. The
British invaders brought their own African slaves with them and established
plantations on land grants. Today nearly 90% of the population descend from the
slavery years of that early period.

16

The nutrient-rich currents of the Atlantic Ocean and the gulf stream make the
Bahamas the ideal haven for a variety of large predators: tiger, lemon, bull,
Caribbean reef, nurse and great hammerhead sharks. The reefs at the edge of the
gulfstream in the western Bahamas are often covered in corals and sponges and
teaming with schools of jacks, snappers, grunts, countless tropical fish. They are one
of the best places for meeting sharks, turtles, rays, and wild dolphins. Tiger beach at
West End near the little Bahama Banks has become a sanctuary for Tiger sharks.
Bimini, the most western island at the edge of the gulfstream combines two habitats:
mangrove forests in the north providing a safe, shallow ecosystem for juvenile -
mostly lemon- sharks, and the gulf stream-fed reefs and sandy shallows in the
west to give them a rich and healthy environment to live in as adults.

Ernest Hemingway with his wife
Pauline and three sons on a dock in
Bimini in 1935

The Great hammerhead and Bull
shark belong to Bimini's regular
visitors. Bimini is also a favorite spot
for anglers from the US who in the
tradition of Ernest Hemingway go
after the tuna, marlin and dolphin
fish. Cat Island, at the east side of
the Banks, at the edge of the Atlantic
has recently become a sanctuary of the Oceanic white tip shark. This legendary
pelagic shark can be visited while the dive boat is drifting in the clear deep and blue
water of the Atlantic in the southern part of the island.

Link:
https://en.wikipedia.org/wiki/Bahama_Banks

17

NURSE SHARKS: ‘LAZY’ BUT EFFICIENT SURVIVORS

The nurse shark (Ginglymostoma cirratum) is not the most popular shark on the list
of underwater photographers. They simply miss the elegance of the requiem sharks,
the Carcharhinidae and the hammerheads, the Spyrna. The shark has two small
beady eyes, a broad snout and a small mouth, bracketed by two sensory barbels and
deep oronasal grooves connecting the mouth and the nasal organs. Unlike most
sharks its mouth is located in front of the eyes. During daytime nurse sharks often
congregate on shallow sandy floors at submerged ledges or in crevices of the
reef. They have a brownish spongy body with large rounded pectoral fins that they
use to rest on the sandy sea floor, a long tail and two backward dorsal fins of almost
the same size. Nurse sharks are ovoviparous, meaning that their eggs hatch in the
mother until she is ready to give birth to a large (20-30) number or pups. The size of

the pups is around 30 cm.
Nurse shark seem a bit dull and
sluggish, a reason why they are
sometimes considered as the "couch
potato" of the sharks. The ones we
met at Bimini were often grouping
together on the sand, waiting for a
moment to snatch a small piece of
fish from the baiting box (see insert).
Sometimes pushed away with a pole
to allow the hammerheads a free
access. Nevertheless, the shark is an
efficient hunter, able to crush shells of
mollusks with its small razor sharp
teeth. With its small mouth its
capable to suck in its prey with a
short, violent influx of water. A nurse shark is seldom seen chasing its prey, probably
because it takes advantage of dormant fish during the hunts at night, which would
otherwise be too fast for the shark to catch. Similar to the white tip reef shark it is
able to respire while stationary by pumping water through the mouth and
gills. Taken together these facts suggest that nurse sharks spend relative little
energy. Its metabolic rate, even while swimming is estimated to be only 18 percent of
a similar measurement in the high-performance Mako shark. So, the general
impression is that nurse sharks are well adapted to their environment and successful
survivors due to their low energy expenditure, efficient hunting strategy and large
number of pups. Which probably also explains why they are still one of the most
prevalent sharks in tropical and sub-tropical waters.

Link:

https://www.sciencedaily.com/releases/2016/02/160201220322.ht
m

18

MANGROVES. THE FORGOTTEN HABITAT

Mangrove habitats or mangals are woods along the shoreline that have adapted to
the intertidal movement of saltwater. In some mangrove swamps saltwater mixes
with sweet water from rivers diminishing the degree of salinity. Mangroves do
not enjoy a great popularity among tourists, for obvious reasons. The hot and
humid air and the almost impenetrable swamps and numerous bugs are the major
causes that they will not score high on a list of pleasant holiday locations. Their low
appreciation and the destroying of mangrove forests are expressed in the title of this
article that I borrowed from Jeremy Stafford-Deitsch's wonderful book on

Mangroves.
Mangroves are not the first
choice of UW photographers,
although the tidal zones offer
interesting opportunities for close
up or even macro shooting for the
snorkelers. Small fish like gobies,
blennies, cardinal fishes and
snappers are often hiding in the
mangrove roots. Mangroves are
also interesting for taking ‘over
under shots’. For example
a school of snappers, perhaps
even a Caiman crocodillus or a
juvenile shark under the surface,
and some lovely mangroves above
the surface. For people interested
in topside pictures, wet suit
booties, a pair of small
binoculars, a telephoto lens for
more distant objects like birds or
mudskippers are recommended
Top: Rhizophora mangrove of Bimini. Below:
various types of mangroves in the tidal zone.

And an insect repellent! The most easy entrance is from the sea in a small boat.
Which allows you to visit two worlds, the intertidal area and the forest itself, at least a
part of it.
From the point of view of ecology and biodiversity mangrove forests are a true
marvel. They are the habitats of numerous fish, rare birds, crabs, insects, plants and
flowers. Birds find an enormous food reserve in the form of worms and small crabs in
the mud floors. The mangroves form a highly complex world, and the exploration
of living species in the mangroves is still in its infancy. A mangrove forest is also a
magic world with their human-like trees, funny roots and the strange sounds

19

echoing in the silence. Perhaps the mangroves whispering to each other, like Tolkiens
trees in Fangorn forest?
Locations Richest mangrove forests are found on the eastern hemisphere along the
coasts of East Sumatra, North East Borneo, North East Australia, Papua New
Guinea, and in the Ganges Delta along the gulf of Bengal. But there are also
numerous mangroves on the Western hemisphere in the Caribbean, Bahamas (on
Bimini mangroves are found in a fringed lagoon) and the Americas.
Zonation The variety of mangroves is enormous: different genera are connected
with different tidal zones (see picture above). Red mangroves are found mostly at the
seaward edge followed in succession by black, white and buttonwood mangroves
more land inward. In each tidal zone the mangroves have adapted to the
environment dependent on the amount of immersion during high and low
tide. Some mangroves are fully inundated by all high tides, others partly
inundated and still others only by exceptional high tides. Mangrove seeds (also
called propagules) look like elongated beans. They are buoyant and therefore
suited to water dispersal. They grow on the parent mangroves until they are about 3
cm long and then drop they into the water when the tide is in. The seeds
are viviparous: they germinate while they are still on the parent tree. that will often
carry whole bunches of these seeds.
Mangrove roots Mangroves can survive because they have learned to filter out
much of the salt even when it is absorbed in their leaves or roots. Especially their
roots are crucial in surviving in the salty and anaerobic mud floors of the mangrove
swamps. They allow mangroves to absorb gases directly from the atmosphere. For
example, mangroves of the genus Avicennia (mostly black mangroves) that are found
on higher grounds have developed aerial roots looking like thin pencils, often
surrounding the base of the tree. The same holds for the Sonnerata genus
which root resembles a peg or snorkel sticking up. The Brugulera genus has strange
rootlooking like knobbing knees. Most conspicuous perhaps are the red mangroves
(or Rhizophora) that have developed spread legs (also called prop roots or stilts) that
stabilizes the tree (see picture above taken on Bimini). It is said that aboriginals of
the Northern Australian coast believe that the prop rooted mangroves once walked
from the sea to the shore. Some Rhizophora trees have also developed cascades or
‘curtains’ of aerial roots hanging from the tree tops.
Mangroves in danger Mangrove forests are in danger. One factor is big tourism
and clearance of mangrove forest for recreational parks en jetties for cruise ships.
And tourism inevitably brings in rubbish and plastic drifting everywhere. Oil spill
from off shore companies, industries and tankers flushing out their tanks in sea are
devastating for mangrove habitats. And then there is the clearing of mangrove forests
to make place for aqua cultural ponds for fish, shrimp and prawn, often subsidized
by local governments. Another area in danger is the Sundarban Reserve Forest
located in the south-west of Bangladesh adjoining to the Bay of Bengal. This immense
forest is threatened by climate change, in particular the rising sea levels and floods
entering the delta and its mangroves. The area contains not only crocodiles but also
the rare Bengal tiger whose habitats are shrinking due to the floods. Villagers now

20

become aware that the mangroves are their protection and have stopped cutting
down the trees for charcoal production, and instead have started new mangroves.

Sources and links:
Jeremy Stafford-Deitsch. Mangrove. The forgotten Habitat.1996 Immel
Publishing London.
Tomlinson, P.B. (1986). The Botany of Mangroves. Cambridge University Press,
Cambridge.
https://en.wikipedia.org/wiki/Mangrove
https://www.youtube.com/watch?v=OH9kF2Vtz-A

21

FEAR OF LARGE PREDATORS MAY AFFECT THE FOOD CHAIN.

Fear of large predators living in the wild was one of the reasons why humans have

attempted and largely succeeded in extirpating many large predators on the planet.

But apex predators play a critical role in conserving biodiversity. Marine biologists

call this ‘ecosystem service’. Since apex predators are op top of the food chain, their

presence affects not only the smaller predators (their potential prey), but also the

species at lower levels of the food chain. It’s probably not only the physical presence,

but also the fear of a larger predator (e.g. a wolf or a big dog) that prevents smaller

predator(a raccoon) to start foraging on their favorite prey (a small crab) in certain

territories. Which of course is advantageous for their prey, but not so advantageous

for the crabs potential victim (a

sea snail) at a lower level of the

food chain. Biologists call this

a trophic cascade (see picture at

the left).

The hypothesis that fear could

affect the cascade in the food

chain was recently tested by

Canadian biologists from the

University of Victoria, BC.

They investigated if fear of dogs

could change foraging by raccoons

living on coastal Gulf Islands in

BC, in particular their foraging on

marine species as crabs and small

A trophic cascade: the red and green arrows illustrate
the negative and positive effects of predator prey
interactions at various levels.

fishes living in the tidal ponds along the shoreline (the dog is the raccoons old
enemy). But they also looked at effects further down the cascade: on the crabs
favorite food. They did not use real dogs, but playbacks of dog barking and howling ,
and compared those with non-predator sounds of harbor seals. Using month-
long playbacks, the dog barking (but not the sounds of seals) drastically reduced
raccoon foraging to the benefit of its potential prey (crabs an little fish), but at the
cost of their prey the snails. The amount of little fish and crabs in the tidal zones
returned to that of islands where raccoons don’t exist. The investigators conclude that
their findings could be important for conservation of wildlife, in particular of the
large carnivores and their role in re-establishing a ‘landscape of fear’.

Justin P. Suraci et al. Fear of large carnivores causes a trophic cascade. Nature
Communications. (23 Feb 2016)

Laundre, J. W et al. Wolves, elk, and bison: reestablishing the ‘landscape of fear’ in
Yellowstone National Park, U.S.A. Can. J. Zool.2729, 1401 (2001)

THE SHARK IN CAPTIVITY

Keeping sharks in million liters tanks has become a ‘must’ to attract visitors to an
aquarium. For example, the famous Georgia Aquarium is a public aquarium in
Atlanta, Georgia, USA. It houses several thousand species, all of which reside in 10
million US gallons of marine and salt water. For long it was the largest aquarium in
the western hemisphere. But then in 2012 it was surpassed by Marine Life Park in

Singapore. Both aquaria also have
sharks swimming around behind
large panoramic windows, creating
for the visitors the impression that
they are actually among them in the
ocean. They are also the place to take
your kids to in the week-end. They
will love it, watching the sharks while
clutching daddy's or mummy's hand.
But many species of sharks don’t
seem to do very well in captivity. One
factor could be the stress of
transportation. Restricted space plays
a second role, although modern
saltwater aquariums have a great deal
of room to move around. Nevertheless many sharks end up dying within a year after
their capture. Even the species that are released after a while in the open sea have
difficulty with surviving longer than one year. Best chances for survival have smaller
more docile sharks like cat sharks and nurse hounds and epaulette sharks. Probably
because these species are more territorial. And even some larger species like sand
tiger and leopard sharks. Some of the greater aquaria also managed to keep tiger
sharks in life for several years.
The larger a shark species can grow, the less likely it is that they will successfully
survive in captivity. Recently, a female Great White Shark reached a new record;
surviving 44 days in a million-gallon tank housed at Monterey Bay Aquarium in
California, eating four pounds of salmon, mackerel and one sardine (see picture
above). But following its release it died a week later. Some time
ago, another showcase of a great white shark held in captivity in an aquarium in
Okinawa also died shortly after its delivery by fishermen who caught it in their nets.
Why do sharks do not well in captivity? Like the goldfish in the little pond on my
balcony, some of which must now have reached the age of twenty years, and still
seem to enjoy their little biotope. This is their world. Not so with sharks. One reason
could be the restriction of their migratory range. Most predator sharks
swim hundreds of kilometers within a matter of days. This exercise and freedom is
essential to their contentment. Another factor could be that sharks, unlike dolphins
and orca’s, have a limited capacity to interact with humans. Probably because they
are the offspring of a different and much older branch of the evolutionary tree of
species that depend on inborn reflexes to survive in that great ocean.

23

GREENLAND SHARKS CAN LIVE AT LEAST 300 YEARS
The Greenland shark (Somniosus microcephalus) an iconic species of the Arctic
Seas can reach 5 meter in total length, with a life span well beyond those of other
vertebrates. The species is large yet slow-growing, with a rate estimated to be around
1 cm per year. It is a slowly moving shark with a preference for deep water, but is
sometimes also seen scavenging around fishing boats. The shark is an apex predator
like the great white shark, but it is seldom seen hunting other species like sea lions,
which is probably due to its ice cold environment. While the Greenland shark is one
of the world's largest sharks, it is one of the least understood animals on our planet.
Its general biology and way of life have been a mystery to biologists for many years.

Recently an international team of marine biologists from the University of
Copenhagen's Department of Biology, has revealed one of this shark's many secrets
(Nielsen et al. 2016). They investigated 28 female species (varying between 81- 502
cm) collected in Greenland between 2010 and 2013. The Danish lifespan study was
based on a method called radiocarbon dating. Radiocarbon - also called 14C- is
constantly being created in the atmosphere by the interaction of cosmic rays with
atmospheric nitrogen. The resulting radiocarbon combines with atmospheric oxygen
to form radioactive carbon dioxide, which is incorporated into plants by
photosynthesis; animals then acquire in their tissue 14C by eating the plants. Because
14C decays at a known rate, the proportion of radiocarbon left in tissues can be used
to determine how long it has been since a given sample stopped exchanging carbon –
the older the sample, the less 14C will be left.
Normally radiocarbon is derived from calcified bony tissue, but since this is absent in
the Greenland shark, Nielsen et al used the center of its eye lens. This does not
change from the time of a shark's birth, and hence allows the tissue's chemical
composition to reveal a shark's age. They further used the bomb pulse as a time

24

marker. This refers to a sudden increase of carbon-14C produced by nuclear tests in
the 1950s—specifically, its incorporation into the eye during development—to
determine the age of Greenland sharks. The bomb pulse has often been used as a
time stamp to validate the age of marine animals.
The smallest sharks in the sample (less than 2 meter) showed the highest radiocarbon
levels, implying that their dates of birth would be close to bomb pulse onset (around
1960; when bomb-produced radiocarbon becomes detectable in the chronology of
the Northern Atlantic species). The age of the prebomb sharks was estimated by using
a calibrated time scale. This is a statistical method to predict the most probable age
on the basis of the actually measured radiocarbon in the eye lens, under a set
of biological and environmental constraints. Such as climate and individual
variations. size at birth, rate of growth etc.
Investigators suggest that the oldest of the animals that they sampled had lived for
nearly 400 years, and they conclude that the species reaches maturity at about 150
years of age. If their oldest shark indeed lived 392 years, its date of birth must have
been around the time when the first Dutch colonists landed on the East Coast of the
United States, shortly followed by the foundation of New Amsterdam, renamed New
York on September 8, 1664

Source and links:
Eye lens radiocarbon reveals centuries of longevity in the Greenland shark (Somniosus
microcephalus). Julius Nielsen et al. Science, 12 Aug 2016: vol. 353, issue 6300, pp. 702-704
http://phys.org/news/2016-08-winner-longest-lived-vertebrate-award.html
http://science.sciencemag.org/content/353/6300/702
http://www.sharksider.com/greenland-shark/
https://en.wikipedia.org/wiki/Radiocarbon_dating

25

FACING THE ABYSS: FREE DIVING AND ITS RISKS

Free diver Natalia Molchanova who died in an diving accident some years ago
Free diving for commercial purposes already existed in ancient Greece when sponge
divers descended in the Mediterranean to collect sponges used for bathing. This
profession continued for many centuries thereafter.
The early start Initially, the divers had no fins, diving mask or goggles and just
jumped in the water with a heavy flat stone of 15 kg, called Skandalo petra, to
descend rapidly. The sponges were already spotted from the boat using a
cylinder. When sufficient sponges were collected the basket with sponges and the
diver with stone were pulled on board. Greek divers could remain underwater for
around 3- 5 minutes at a depth of 20-30 meters. The skandalo petra method is still
used in modern times by free divers trying to break records. They are allowed to use a
nose clip but no fins or diving suit. Sponge diving remained a typical Greek
profession carried out up to the 20th century in Florida waters. But then the divers
used helmets and suits that received compressed air via an air hose connected with
a motorized or hand driven pump on deck of the boats. Another ancient form of
free diving was that of the Japanese Ama’s. young and also older women diving for
oysters with pearls along the Japanese coast. Either in the nude or dressed in white
gowns. Many of these divers must have suffered from decompression illness, since
they had to do many dives a day to make a profit. There are reports of ancient divers
in the 13th century that used polished tortoise shells as a lens in their self made
goggles. Polynesians seem to have used wood or bamboo goggles that would trap air
to create a viewing area while submerged. Once introduced to glass, they applied
glass lenses to their goggles.

26

Competitive free diving Although modern competitive free diving is not
commercial, it does force the diver to push the limits of the human body and
sometimes overstepping these limits. In 1976 the Frenchman Jacques Mayol,
became the first man to break the 100m dive mark. Mayol also introduced yoga and
meditation into free diving as a means to prepare his body for the forthcoming
physical stress. There are several categories of free diving, each with its own records
and champions. There is STATIC APNEA (in a pool), DYNAMIC APNEA (swimming
horizontally as far as possible, with or without fins), VERTICAL DIVING (with or
without fins, using constant weights or variable weights) and NO-LIMITS APNEA (any
means allowed during descent and ascent). Most ‘natural’ seems the vertical apnea
without fins or weights. But this will require a lot of muscle power and consequently
more oxygen and carbon dioxide buildup. Fastest way to get down and up is the no-
limits apnea. Here the diver uses a weighted sled to descend rapidly and an air-filled
balloon to return fast to the surface. It resembles a bit the skandalo petra
method. This method is certainly the most risky because if a slight detail goes
wrong, it could mean the end of the diver. Ideally, a diver trying to break a record in
this category in the open sea should first practice the stages of descent and ascent in a
controlled environment. For example a submarine escape tower, although these are
often not higher than 30 meters. Even better would be a wet hyperbaric chamber
allowing to control the hydrostatic pressure and to monitor the divers physiology.
Records The skandalo petra free diving record was set at 112 m by Andreas
Güldner in 2014. The current world records for static apnea are 11 minutes 35
seconds and 9 minutes and 2 seconds for men and women, respectively. The current
world records for non-limits apnea are 702 feet (214 meters) and 525 feet (160
meters) for men and women respectively. Deepest man on earth in this category is
Herbert Nitsch, with 214 meter. Deepest women in the same category is Tanya
Streeter with 160 m. A tragic victim in the same category was the beautiful
champion free diver Audrey Mestre who dove 561 feet trying to break the world
record. But the 28-year old French woman did not make it back up alive in October
2012. The lift bag that should have taken her back to the surface did not work,
because someone had forgotten to fill the connected air bottle.
On 17 November 2013 Nicholas Mevoli an American free diver in the category ‘with
fins and constant weights’ attempted a dive to 72 meters (236 ft) on a single breath in
the Bahamas but later collapsed due to pulmonary edema. Current free dive
champion in the same category is Alexey Molchanov who reached 128 m. His
mother Natalia Molchanova who held the women record of 101 meters in the same
category died in a diving accident last year in Spain (see picture of Natalia above).
These are truly awesome numbers (and accidents), as are those in the other
competitive categories. Some scientists believe that free divers have learned to ‘push
evolutionary buttons coming from a period earlier in evolution'. Probably still
functional during the birth process, when it’s important for the fetus to slow down to
survive a perilous passage through a birth canal that restricted blood flow.

27

Physiology The physiology of the free diver is well investigated. There are several
effects working in succession on the body of the diver during the descent. The dive
reflex comes first, after the face touches cold water. This implies that heart rate and
metabolism slow down. The effect of this reflex is greater in cold water than in warm
water. The arteries in arms and legs constrict, pushing more blood back in the body
and vital organs like lungs and liver. Decrease of heart rate and blood pressure also
lowers cardiac output. At 20 meters divers without weights usually reach negative
buoyancy. With increasing depth the pressure around the thorax increases
dramatically, and so the lung volume. At 100 meters lung volume is only 1/10 of its
surface volume. The smaller volume will increase the partial pressure of nitrogen.
carbon dioxide (CO2) and oxygen (O2) in the lungs. Miraculously, the lungs do not
collapse, probably because blood plasma forced in the thoracic cavity compensates
the decreased volume of the lungs. During the descent the free diver must resist the
trigger point: the moment when he/she feels a strong urge to breath, even when
the diaphragm that separates the thorax from the abdomen, starts to
contract. During the ascent there are two factors working on the divers physiology,
time and volume increase of the lungs. The resultant rapid change in the pressure of
gasses in the body and brain are essential to survive in the relatively short period to
reach the surface.
Risk factors The main hazard of repetitive free diving, as it was carried out by the
old commercial divers, is the buildup of nitrogen. Although their bottom times are
short and their dives rather shallow, there is a buildup of nitrogen with each dive that
may cause the bends. Competitive divers sometimes experience euphoric and ‘spaced
out’ feelings, probably the result of the higher pressure of nitrogen but also the lack
of oxygen. The same factors can lead to a blackout or difficulties with carrying out
simple motor acts like opening a valve, at greater depths.
Hyperventilation is also a risk factor. It does not increase the amount of oxygen in
the blood, but washes out the carbon dioxide, which is the major trigger of the need
to breath. Shallow water blackout is one of its greatest dangers. It is most likely to
occur during ascending in the last 10 meters, when air in the lungs expands rapidly.
This may cause the O2 level to drop into the diver's blackout zone before the CO2 can
rise enough to force the diver to resurface to breathe. Being fit, a large lung volume
and having learned how to bypass the urge to breath, are factors that can extend the
time that one can hold his or her breath. Some divers also practice meditation prior
to a deep dive to relax. But competitive free diving remains a very dangerous sport
where the line separating a safe dive and a fatal accident remains very thin.
The experienced divers are aware of the dangers and have found ways not to cross
that line. But they or their team members remain humans, and likely to make errors
of judgment.

28

Sources and links:
Wong, R. M. (1999). "Taravana revisited: Decompression illness after breath-hold diving".
South Pacific underwater medicine society journal 29 (3). ISSN 0813-1988
Schipke JD, Gams E, Kallweit O. Decompression sickness following breath-hold diving. Res
Sports Med. 2006 Jul-Sep;14(3):163-78.
http://www.freedive-earth.com/learn-freedive/skandalopetra-CMAS
https://en.wikipedia.org/wiki/Freediving
https://en.wikipedia.org/wiki/Alexey_Molchanov 122 meter
http://freedivingexplained.blogspot.nl/2008/03/basics-of-freediving-freediving.html
http://divewise.org/education/freediver-blackout/
http://nautil.us/issue/22/slow/the-impossible-physiology-of-the-free-diver
http://edition.cnn.com/2015/08/06/opinions/pollock-free-diving/
https://vimeo.com/70997378

29

LIFE OF A GOBY

Gobies are small fishes varying in size between 2 and 20 cm. They belong to one of
the largest fish families, the Gobiidae comprising more than 2,000 species in more
than 200 genera. Best known is the subfamily of Gobiinae, also known as the true
gobies, that contains more than 60 genera and 1120 species (note that the biological
hierarchy spreads from: family→ subfamily →genus →species). As such, gobies are
a good example of the amazing variety in adaptations of some fish species to its
environment.

Most gobies have a large head
and eyes, two dorsal fins, large
pectoral fins, and pouting
cheeks. They have an elongated
transparent or colored body
with scales, often covered with
bands or patches. Most species
have fused pelvic fins that form
a disc-shaped sucker somewhat
like the dorsal suckers of
remoras. But the goby uses it to

A goby with cleaner shrimp near the mound of its burrow

attach itself to rocks or coral branches.
Gobies are found everywhere over the world in tropical and temperate, brackish and
freshwater environments. Most species seem to prefer shallow habitats like tide
pools, coral reefs, mangrove swamps (where you find the mud jumpers) and sea grass
floors. A special genus from the subfamily of Gobiinae is Bryaninops, the sea whip
(or whip-coral) goby from the tropical Indo-Pacific waters. This genus can be split
up in 16 species one of which is Bryaninops yongei. This species uses gorgonians and
black coral as its host (Cirrhipathes anguina). The whip coral goby has a semi-
transparent head and body and it spawns on its host, the gorgonian.
Gobies usually live in male-female pairs. Many of them are bottom dwellers with
habitats in the vicinity of a sandy bottom. Here there construct burrows (holes in the
sand), using their mouths to dig into the sea bottom and by fanning away sand. The
burrows are used as a hiding place as well as nests for spawning. The entrance of
the burrows are blocked with small pieces of coral or rubbish. The goby also builds
a mound -a small hill of sand- over the entrance of their burrow. Sometimes the
burrow is shared with a little shrimp (see picture above). Initially male gobies are
more active with maintaining the burrow. But after spawning the female takes over
the maintenance, while males guard the eggs and provide them with oxygen by
fanning water over them.
Some smaller male gobies play a interesting role during the process of spawning.
Since female gobies seem to prefer large males, the small guys must find a strategy to
deliver their sperm. This process is also called kleptogamy (secrete fertilization). So

30

the small goby, also called sneaker approaches the spawning place of the official
couple, and waits for the opportunity to release its sperm when the female releases
her eggs. The sneaker often gets away with it, probably because he is small and
hardly distinguishable from females. The sneakers don’t have to go through the
trouble of burrow building, maintenance and parental care. So that’s a clear benefit,
and a way to save energy. But there is also a cost involved: namely the risk of being
attacked or even killed by the larger official male, in flagrante delicto

Source and links:
Patzner, R.A.; Van Tassell, J.L.; Kovačić, M.; Kapoor, B.G., eds. (2011). The Biology of
Gobies. Enfield.
https://en.wikipedia.org/wiki/Goby
https://en.wikipedia.org/wiki/Gobiinae
http://fishbase.sinica.edu.tw/summary/SpeciesSummary.php?ID=7251&AT=Whip-
coral+goby

31

THE DOLPHIN, MARVEL OF THE SEA

The word dolphin is probably derived from the Greek where δελφύς (delphus) mean
‘womb’. So the Greeks saw the dolphin as a creature from the sea with a womb.
Dolphins are nearest to human in encephalization, a kind of index used by
behavioral biologists to compare intelligence across different species of mammals.
Meaning that of all mammals, including the chimpanzee the brain size of dolphin
corrected for body mass is nearest to that of Homo sapiens.
The most common species of dolphins are the spinner dolphin ( Stenella
longirostris) and the bottlenose dolphin (Tursiops), often hold in captivity to amuse
the public. The spinner dolphin with its pointed snout is found in off-shore tropical
waters around the world. It is famous for its acrobatic displays in which it spins along
its longitudinal axis as it leaps through the air. The bottlenose is bigger and more
common, an often swims in small groups or pods that can mix with other
pods. Other species are the common dolphin, with two subspecies, Delphinus
capensis and Delphinus delphis, the striped dolphin (Stenella coeruleoalba) and
the spotted dolphin (Stenella attenuata).
Dolphins are smart in locating their prey with their echolocation system. When a
school of fish like sardines is spotted, they trap them and take turns swimming
through the school and just gulp away. Places in the Red Sea were underwater
photographers have a good chance of meeting dolphins are Eilat in Israel, Samadai

Reef and the Sataya lagoon, not so
far from Marsa Alam in the
southern Red Sea. Unfortunately,
the boats that line up in Sataya and
their numerous visitors may spoil
the opportunity to get really close to
the dolphin pods, often consisting of
spinner dolphins.
Dolphins have stimulated human
fantasy and need for symbolism
since ancient times. There are
often described as mystical
creatures that combine two worlds
that of man and fish, somewhat like mermaids. The goddess Aphrodite is often
depicted with dolphins, riding or being accompanied by them. Dolphins were also
messengers of Poseidon the mighty god of the Sea, bringing him lovely nymphs to
inspect. And they were seen as rescuers of humans. Old Roman mosaics often show
dolphins, either in isolation or with gods riding them (see my picture above of
a mosaic taken in Ostia Antiqua in Rome). Sadly, in some places of the world like
the Faroe islands and Japan dolphins are still hunted down and killed by for human
consumption. Which is almost like cannibalism. A cruel and frequently criticized
method is drive fishing, a merciless method of driving dolphins together with boats
into a bay or onto a beach and then slaughter them down. You can witness that in the
dreadful documentary The Cove.

32

Dolphins in captivity Many dolphins and whales like Orcas spend their live in
tanks for our entertainment. Wild whales and dolphins can swim up to 100 miles a
day, hunting and playing. In captivity they have very little space and cannot behave
naturally. A concrete tank can obviously never replace their ocean home. The famous
marine park Sea Word holds around for the 119 whales and dolphins in captivity.
Many of them are taken from the wild. Confining too many animals together in small
tanks, were they usually stay after their performances, can result in stress and

aggression with no possible escape.
Animals liberation activists have
campaigned to free Orcas and put
them back to sea. But this might not
be such a good idea, since the
chances of survival in the wild Ocean
without a herd to support them are
pretty small.
Some people argued that the negative
side of bringing animals into captivity
is out weighted by such benefits as
enhancement of human appreciation for animals, conservation of species and
advancement of knowledge. This argument is similar to that of people that support
Zoo’s that keep wild animals like lions, elephants, tigers and apes. Some have also
argued that the amount of suffering and stress from animals held in such
environments may not differ so much from animals living in the wild where
conditions to survive are much harder than those in captivity.
Helping a dolphin a hand Dolphins are sexually active animals and male
dolphins such as bottle nose dolphins living in the wild are known to masturbate
regularly to climax. One reason might be to flush out sperm that has lost its motility.
Same holds for bottlenose dolphins held in captivity which often have limited space
or partners to play or copulate with. In some cases dolphin trainers help dolphins to
ejaculate, to collect sperm for artificial insemination. Dolphins have already learned
to turn on their back and let the trainer do the 'hand job'. It’s not necessarily
something to get upset about or to think that these animals are maltreated
But the public and newspapers often react shocked when they read or see in the
media that a human person was involved in helping the animal to lose it sperm. And
then easily associate it with ‘animal sex’, a perverted form of human/animal
interactions that can be found on Internet.
To conclude: animal liberators are always on the front row in their protests. Some of
it is justified, and it’s true that some marine parks do not have sufficient space to hold
marine mammals as dolphins or Orcas. The other side of the coin is that many of
them would not survive when set back in the ocean again.

33

Probably the establishment of more
natural and ‘semi-open’ sites to
observe and come close to dolphins is
a much better way of bringing adults
and children in contact with these
wonderful creatures. On these
ecological reefs dolphins can swim
around in a confined environment
offering much more space that the
marine parks. A good example is
the Dolphin Reef in Eilat. Here visitors
have the opportunity to actually observe dolphins up close in their own natural
habitat, where a group of bottlenose dolphins, including some born at the site, carry
on their daily lives of hunting, mating, and playing.
As opposed to a marine park like Sea world, the Dolphin Reef enforces a strict policy
of non-intervention. Dolphins frequently interact with human visitors, but their
behavior is spontaneous and not controlled by humans like in other marine
entertaining parks.

Links:
http://www.pbs.org/wgbh/pages/frontline/shows/whale
s/debate/ethics.html
https://en.wikipedia.org/wiki/Dolphin_Reef

34

THE AMAZING CUTTLEFISH

Cuttlefish are considered to be highly intelligent invertebrates. With the squid,
octopus and nautilus they belong to class of cephalopods (derived from the
Greek κεφαλόποδα meaning head-footers)2. They are not fish but mollusks with
large, W-shaped pupils. Most cuttlefish are around 10-20 cm, but some species like
Sepia apama become much larger like 50 cm-1 meter (not be confused with the
larger squids that can grow to 5 meters). Cuttlefish are amazingly versatile creatures
that can change appearance at will from mimicking floating vegetation or rocks on
the seafloor to its own shape or a member of the opposite sex.
Just like the octopus, the cuttlefish is equipped with eight arms and an ink sac. The
ink is most often used as a ‘smoke screen’. But some species can use the ink
to produce pseudomorphs: black shapes that have roughly the size and form of the
cuttlefish. Cuttlefish have excellent (back-white) vision and they ‘hear’ with their
lateral line, like many fishes do. Surprisingly, cuttlefish also have a beak that looks
like a parrot's beak and that can be used to bite its enemy or prey.

Body plan of a cuttlefish.
1: gonad; 2: stomach; 3: shell
(cuttlebone); 4: mantle; 5: eye; 6a:
long tentacles; 6b: short tentacles;
7: heart; 8: kidney; 9: mantle
cavity (pallial cavity); 10: ink
gland; 11: anus; 12: funnel
(siphon); 13: radula; 14: beak; B:
internal shell (cuttlebone).

The eight arms of the cuttlefish are mainly used to grasp its prey after it has
captured it with its two elongated tentacles, that shoot rapidly from a pocket at the
base of the arms to grab the prey. To jet away from a predator the cuttlefish sucks
water into the cavity of its mantle and then uses its strong mantle muscles to expel
the liquid with great force, driving the cuttlefish in the opposite direction.
Its fins, looking like short fluttering skirts are used for mobility in all directions, up
and down forward and backward.
The cuttlebone is an unique internal shell with an interesting construction. The shell
has both gas-filled forward chambers and water-filled rear chambers. The porous
shell serves to control its buoyancy, although it can take hours for the cuttlefish to
change its density. The cuttlebone is rich in calcium and is often sold in pet stores as a
nutritional supplement for birds.
During mating the male grabs the females tentacles, turns her so that they are face to
face. He then uses a specialized arm to insert sperm (called spermatophores) into an
opening in a sac near the female's mouth. When the female has found a safe place to

2 Cuttlefish belong to the order of Sepiida. Squids belong to a different order of cephalopods called Teuthida.
Squid as food is also known as calamare. Squids are found abundantly in certain areas, and provide large
catches for fisheries. The often grow larger than cuttlefish.

35

put her eggs, she also empties the sac with the spermatophores. She then uses her
arms to wipe the stored spermatophores over the eggs. The male must often fight off
male rivals before he can consider the female as his ‘own’. But he also can use
camouflage and disguise himself as a female cuttlefish, either to approach a female or
to fool a larger competitive male.

Esthetic view of a cuttlefish. Author
unknown

Probably the most fascinating
quality of the cuttlefish is its
ability to change color. The reason
why they are often called
chameleons of the sea. It has in its
skin around 200 chromato-
phores per square millimeter:
elastic sacs containing different
pigments like red, yellow, brown, and black. Bands of muscles radiate from each
chromatophore and are controlled by neurons in the motor centers in the brain. The
muscles can also be used to change the texture of the skin (e.g. from smooth to
rough). When seeking for a mate, a male cuttlefish will sometime show contrasting
zebra displays. Color patterns are also used to communicate with another, to warn of
potential predators and competitors and as camouflage. Cuttlefish swimming in
groups often change colors in rapid succession, perhaps as a way to communicate
with other members of the group.

Links:
https://en.wikipedia.org/wiki/Cuttlefish
http://www.pbs.org/wgbh/nova/camo/anat-nf.html
http://vetnetwork.net/ext_clients/chastain/pca.php?article_id=521

36

THE PYGMY SEAHORSE

The word seahorse is derived from the Greek hippocampus, which is a junction of
the word hippos meaning horse and campus which does not mean ‘monster’ like
some sources claim. Campus or kampois probably derived from the Greek verb
kampto (meaning: to bend) or kampti (meaning: bent). So it literally means ‘bent
horse’. But in the ancient Greek world hippocampus was also used as a designation
of a mythological sea monster with the head and body of a horse and the tail of a
dolphin.

A seahorse is a bony fish without scales.
During mating the female seahorse deposits
numerous eggs in the pouch of the male,
that fertilizes and bravely carries the eggs for
a month or so until the minuscule seahorses
are ready to leave the pouch. See the amazing
video below* of a laboring daddy seahorse to
give birth to swarms of babies. The seahorse is
excellent in camouflage and very difficult to
detect among the branches of a gorgonian
where they often gather in groups of around
20-30 individuals.
The pygmy seahorse (Hippocampus
bargibanti is smaller than 3 cm, has a short
snout and very long tail. It is found in the
entire central Indo-Pacific area. It
has bulbous tubercles all over its body, that
match the color and shape of the gorgonian
Pygmy seahorse. Picture taken by
Robert Guild

of the genus Muricella. The pygmy's body and tail resemble the branches and stem of
the gorgonian, while the tubercles resemble the retracted polyps. So its camouflage is
probably more effective when a sea fan is disturbed and retract its polyps, which
concurrently signals the seahorse that is now safe to hide in the gorgonian.
Their tiny proportions and the ability to merge completely with the color of a
gorgonian was perhaps the reason why the pygmies were discovered only in 1970. H.
bargibanti occurs in three color morphs: pink, yellow and orange depending on the
color of the sea fan. Pink or red tubercles are found on the pinkish coral Muricella
plectana and yellow or orange tubercles on the yellowish coral Muricella
paraplectana.
Does the seahorse choose a home that matches its color, or does it change its color to
match its home? This question was solved when investigators found that young
yellow pygmies that were born and raised in yellow gorgonians in an aquarium,
changed their color to red when they migrated to a pink-red gorgonian.

37

It’s hard to give an estimate of the total number of pygmy seahorse and population
trends, but many are caught and dried as part of traditional Chinese medicine that
believes in its power to cure all kind of physical troubles.

Source and links
Froese, Rainer and Pauly, Daniel, eds. (2006). "Hippocampus bargibanti" in
FishBase. December 2006 version.
*https://www.youtube.com/watch?v=Q3CtGoqz3ww
https://en.wikipedia.org/wiki/Hippocampus_bargibanti

38

SNIFFING YOUR WAY BACK HOME: OLFACTION CONTRIBUTES TO
PELAGIC NAVIGATION IN SHARKS

How sharks navigate in the great oceans has always been a mystery. Terrestrial

navigators use cues like earth rotation and the position of the sun to navigate. Cues

that are difficult to perceive by sharks swimming a greater depths in the oceanic

currents. Many type of pelagic sharks, like tiger sharks, great whites and

hammerheads have extraordinary navigational abilities and can find their way in the

big oceans to destinations often hundreds of miles away. Their migratory paths to

their selected locations also seem to follow almost straight lines .

Investigator Andre Nosal from

the Scripps Institution of

Oceanography of La Jolla

recently discovered that

leopard sharks Triakis

semifasciata follow their nose.

Leopard sharks were captured

alongshore, transported 9 km

offshore, released and acous-

tically tracked for

approximately 4 h each until

the transmitter released.

Eleven sharks were rendered anosmic (nares occluded with cotton wool soaked in

petroleum jelly); fifteen were sham controls. The controls appeared to follow almost

straight paths back to the shore. In contrast, anosmic sharks followed more tortuous

and random-like paths. So it seems that these sharks rely on their olfactory bulbs in

tracking a dynamic chemical environment and linking locations in olfactory space.

Sources:

Nosal AP, Chao Y, Farrara JD, Chai F, Hastings PA (2016) Olfaction Contributes to
Pelagic Navigation in a Coastal Shark. PLoS ONE 11(1)

http://news.nationalgeographic.com/2016/01/160106-sharks-leopard-smells-
navigate-oceans-animals-science/

39

CHEATING FOR SURVIVAL; THE FALSE CLEANER FISH

Mimicry is one of the miracles of animal adaptation. It’s a form of camouflage used
by various animal species to deceive a predator or a prey. Basically it can take two
different forms, defensive or aggressive. An example of defensive mimicry is a
harmless snake that mimics the colors of the deadly snake as protection against
potential predators. So in defensive mimicry, the mimic generally benefits from
being treated as harmful.
Aggressive mimicry is just the opposite. It’s a form of mimicry in which predators or
parasites mimic a harmless model, allowing them to avoid being correctly identified
by their prey or host. A example is the false cleaner fish (Aspidontus Taeniatus) also
called the saber-toothed blenny. This little fellow mimics the bluestreak cleaner
wrasse (Labroides dimidiatus) found on coral reefs in the Indian Ocean and Pacific
Ocean. The real cleaner moves dead skin and parasites form the scales of its client
fishes that line up in cleaning stations along the coral reefs. Not so with the mimic
that occasionally may tear away portions of the scales or fins from the client. It not
only looks like its model, but even cleverly mimics the cleaner's dance. The
only difference are the more pointed lips with the enormous canines that sit in its
lower jaw. Interestingly, a side effect of its mimicry could be also be defensive. Some
predators like groupers that normally feed on various fish at a cleaner station, seem

to spare the real cleaners, and
therefore also their mimics.
The success of A. Taeniatus is based on
the fact that the mimic is rare compared
to the genuinely symbiotic cleaner fish.
When too many or too aggressive
cleaners show op on cleaning stations,
they may spoil the foraging of the real
cleaners. The clients will then become
nervous and may even leave the
cleaning station. This will screw things up, not only for the clients and the genuine
cleaners but also for the false cleaners. For the same reason A. Taeniatus will attack
only 20% of its ‘clients’, mostly juveniles who have not yet developed the skill to
recognize the false intruders.
A. Taeniatus should not be with confused with a different looking false cleaner, the
bluestriped fanged blenny (Plagiotremus rhinorhynchos). Of this species only
juveniles mimic the bluestreak cleaner wrasse. Adults seem to behave
differently and adopt an alternative color and striping pattern when they conceal
themselves among fish shoals and then dart out to attack other fish or even a diver.

Source and links:

Poulin, Robert; William L. Vickery (7 July 1995). "Cleaning Symbiosis as an Evolutionary
Game: To Cheat or not to Cheat?" Journal of theoretical biology

http://www.fishbase.org/summary/6071

https://en.wikipedia.org/wiki/False_clean4e0rfish

THE WAYS OF AN OCTOPUS

Octopuses have always amazed the world with their intelligent behavior, unique
colorations to adapt to the background, and the way they manage their flexible arms
without getting them entangled. The octopus is an example of advanced cognitive
adaptation, but how its brain (see the yellow part in picture) works still remains a
mystery. The octopus brain does not look at all like brains of other animals. Is has a
huge optic lobe underneath their eyes and a highly developed touch system which
explains their excellent eye sight and sense of touch. It has two memory systems that
follow these two sensory systems: a visual and an tactile memory used to identify

Left: Anatomy of the
octopus

signals in the environment
for attack or retreat. But
also to explore novel
situations. But most
amazing is how the octopus
controls its eight arms.
Two-thirds of the nerve
cells in the nervous system
are located in the nerve
cords of its arms (see
yellow extensions in picture), which makes the eight tentacles function as an extended
brain. The central brain only has to trigger a command to the arms, which then carry
out the full action sequence. Suggesting that the entire movement plan is embedded
in the arm itself and not in the central brain like in mammals. There is no
proprioception, that is neural feedback paths of their movements to the brain, so
movements must be monitored by 'seeing what happens'. Octopuses are also known
to use their arms in battles, by hurling sand and debris to its rivals. Getting to know
the octopus makes it hard to accept that this superb creature is still hunted down to
end up in sea food dishes all over the world.

Source and links

J. Z. Young's "The Anatomy of the Nervous System of Octopus Vulgaris" (1971)

http://cephalove.blogspot.nl/2010/06/view-of-octopus-brain.html

http://www.dailymail.co.uk/sciencetech/article-3214442/Octopuses-fire-
Cephalopods-seen-hurl-shells-debris-rivals-fights-protect-territory.html

41

THE SPERM WHALES SONAR HEAD

Among the whales or Caetaeans there are two prominent families: the balean whales
(Mysticeti) and toothed wale (Odontoceti). Dolphins, killer whales and sperm
whales are all toothed whales. The sperm whale (Physeter macrocephalus) thanks its
name to its enormous head, almost one third of the size of its body (15-18 meters).
It weights around 40 tons. The sperm whales reputation comes from the writer
Herman Melville and his famous novel describing Moby Dick, a great albino sperm
whale and its deadly struggle with the obsessed captain Ahab. Whale hunters of
former centuries must have feared the confrontation with the large headed whale
while chasing it in the choppy seas in their small boats. Sperm whales are now less
mystical than in the days of Melville and can even be visited by snorkelers floating at
the surface with their cameras. Favorite sites are Dominica, Norway, the Azores and
Portugal. Sperm whales can dive to depths of more than 100 meters to find their
prey Which means that they can hold their breath for long periods of time, often
more than one hour.

The sperm whales head with spermaceti organ, junk, distal sac and blowhole

The orca seem to be the only enemy of the sperm whale. In a NOAA study a group of
Orcas was filmed while attacking a herd of sperm whales, in a “wound and withdraw”
strategy. The attacks were violent and lasted for hours. The sperm whales appeared
largely helpless: their main defensive behavior was the formation of a rosette
(‘marguerite’: heads together, tails out). Another marine study verified that during
sleep the whales lie motionless in a vertical position: head or tail up. Their sleeps
seem to last (on the average) only 15 minutes.
The large head of the sperm whale contains two enormous flexible cavities filled with
fluid. On top is the spermaceti organ filled with milkfish sperm-like substance. It
may contain 1500 liter of fluid wax that was used for candles, lamp oil and
ointments. The cavity beneath it, the ‘junk’ or melon, filled with orange colored fatty
substance (see picture). It is assumed that these spaces may serve to control the
buoyancy of the whale. For instance by letting cold water enter the air tubes that run
through the head before a dive, the fluid in the spermaceti organ solidifies and
reduces in volume. But later it became clear that they were also important for sound
transmission. Through the spermaceti organ run two air canals, one to the

42

blowhole and another to the phonic lips in front of the head that connect with the
lungs. The wax like fluid of the spermaceti organ probably adds internal echo of the
clicks emitted by the respiratory organs, while the melon functions like a
transmission and direction station of reflected sounds (see further below).
The sperm whales brain (red spot at the left in figure above) has the largest weight of
all mammals. It weights around 8 kg which is more than the elephant brain (4.7kg)
and much more than the human brain (1.35 kg). But sperm whales have a
lower encephalization quotient (EQ) which is an index estimating the part of the
brain that may be used for intelligent behavior, when body mass is taken into
account. Here the sperm whale ‘scores’ much lower than its smaller toothed whale
nephew the dolphin. Little is known about the specific functions of the sperm whales
brain. Its main 'intelligent' function as described in current literature is to serve and
steer its refined echolocation system located in that enormous forehead. Used
either to locate its prey, or to communicate with members of its pod or clan. Most
conspicuous in the sperm whale brain are the thick cranial nerves that innervate
muscles in its huge forehead and the facial nerve that controls the muscles of the
blow hole and the large structure in the lower forehead the melon.
In fact, the large head of the sperm whale functions as one big sound producing or
‘sonar’ system. The sperm whale produces ‘clicks’ (sound burst of short duration)
with a pair of phonic lips, also known as "monkey lips" or ‘museau de singe’, at the
front end of the nose, just below the blowhole. The sound then travels backwards
along the length of the nose through the spermaceti organ. Most of the sound energy
is then reflected by the back wall of the frontal sac at the cranium (a sort of sound
mirror) and projected back into the melon, whose lens-like structure further directs
and amplifies it (see picture). So the temporal pattern of multiple clicks produced
by the sperm whale results from reverberations within the nasal complex of the
whales. High frequency clicks are used for location and homing in on the prey at
larger distances, and low frequency clicks for social communication at closer
distances. The echoes are received in fatty structures around the lower jaw, from
where they are transmitted to the middle ear via a continuous fat body to the auditory
cortex in the brain.
Sperm whales swim in small social units or pods and several pods may form larger
groups or clans distributed over a much larger area. Recent studies have shown
that families and clans have their own 'dialect': typical signatures of sound bursts
called codas. For example, a ‘5R’ coda is one in which five clicks are regularly spaced,
while a ‘1+1+3’ coda sounds like ‘click-[PAUSE]-click-[PAUSE]-click-click-click’ with
longer gaps between the first two clicks followed by three clicks in rapid
succession. Using these codas sperm whales recognize vocalizing individuals of other
social units that share a similar dialect. Next to clan codas sperm whales also
produce and recognize individual codas to identify individuals in their own pod and
smaller families within a clan. Calves learn to produce and recognize codas in their
infancy, similar to human babies learning to babble. This learning may take years to
perfection.

43

Sources and links
Whitehead, H. (2003). Sperm Whales: Social Evolution in the Ocean. Chicago:
University of Chicago Press. p. 4.
Oelschläger HH1, Kemp B. Ontogenesis of the sperm whale brain. J Comp Neurol. 1998
Sep 21;399 (2):210-28
Rendell L., & Whitehead H. Vocal clans in sperm whales (Physeter macrocephalus).
Proc Biol Sci. 2003 Feb 7, 225–231
Marine Mammal Science, 2011 (NOAA) Current Biology, 2008.
http://rsos.royalsocietypublishing.org/content/3/1/150372https://en.wikipedia.org/wi
ki/Sperm_whale
https://en.wikipedia.org/wiki/Animal_echolocation

44

ABOUT WHITE AND BLACK TIPPED SHARKS
A good way to identify sharks is to use a guide where you will find most of the
species and subspecies with their official names and appearances. I like
these 'taxonomies' because they give you an idea of the complexity of our evolution,
and the wonderful variety of species. But they can also be tedious, because you will
have to go through the whole scale of class→ order→ family→ genus→ species. And
the features needed to identify a specific shark such as its teeth are not always
obvious. To keep things simple I here focus on the color of the tip of the fins of some
common sharks. So we have white tipped sharks and black tipped sharks.

Silver tip shark from the Sudanese Red Sea
Although these sharks are all members of the family of Requiem sharks or
Carcharhinidae, some may still belong to a different genus, that is a different
subcategory of the family. Here we go:
White tips The two most popular species of white tips of the Indo-Pacific sea of
Genus Carcharhinus, are:
1. Oceanic white tip (C. longimanus) rounded dorsal fin at its apex, broad and
long pectoral fins, found offshore and along steep drop offs. A bold shark that often
closes in to or bump divers.
2. Silver tip shark (C. albimarginatus) conspicuous white-silvery ending on its fins.
Found along the deeper edges of the coral reefs. See picture above.

45

3. White tip reef shark (Triaenodon obesus). This shark belongs to the Genus
Triaenodon, with only one species. It has a rat like face, nasal flaps and short blunt
snout. Often in shallow water. Slender body, allowing the shark to wriggle
itself through tunnels or crevices in the reef wall , when its hunting smaller fishes at
night. The white tip reef shark swims with strong undulations of its body, and unlike
other requiem sharks can lie motionless on the bottom, often with a pack of other
white tips, and pump water over its gills for respiration. A shark that is often found
at the same location on a reef.
Black tips (genus Carcharhinus): 3 species:
1. Black tip shark (C. limbatus). long pointed snout, arched frontal back, looks like
the Spinner shark C. brevipinna that has an even longer snout and more slender
body. See front page
2. Black tip reef shark (C. melanopterus) prominent black tips on all fins,
often in shallow areaand remaining within the same local area for up to several
years.
3. Grey reef shark (C. amblyrhynchos), a very common shark of the Indo-Pacific
reefs. Prominent black edge to tail. Dutch ichthyologist Pieter Bleeker first described
the grey reef shark in 1856 as Carcharias (Prionodon) amblyrhynchos. An older name
of this species was C. menisorrah. The Pacific variety is more aggressive than the
Red Sea/Indian ocean variety. A stiff swimming pattern with pectoral fins down
might forebode a swift attack on an intruder in their territory.

Source and links
Jeremy Stafford-Deitsch. (1987). Shark. A photographers story. (Appendix) Headline
publication. London.https://en.wikipedia.org/wiki/FishBase
https://en.wikipedia.org/wiki/Requiem_shark
https://en.wikipedia.org/wiki/Whitetip_reef_shark

46